<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // 4 1 3 5 2
    var p = new Promise(resolve => {
      console.log(4) // 1
      resolve(5) // 放到微任务队列
    })
    function func1 () {
      console.log(1)
    }
    function func2 () {
      setTimeout(() => {
        console.log(2) // 放到消息队列 5
      }, 0)
      func1() // 2
      console.log(3) // 3
      p.then(resolve => {
        console.log(resolve) // 4
      })
    }
    func2()
  </script>
</body>
</html>